| With the gradual deepening of the reform of the thermal power industry and the continuous rise of the coal price,the coal-fired power plant must develop in the direction of large capacity and high parameters in order to reduce the coal consumption and pollutant emissions.However,the"four tube burst"caused by this,especially the burst of the high-temperature superheater tube,poses a great threat to the safe operation of the unit.During the operation of the 1000MW ultra supercritical unit in Xuzhou Power Generation Co.,Ltd.,the tube wall temperature of the third stage superheater frequently exceeds the limit.The maximum temperature reaches 646℃,which is 15℃higher than the allowable temperature(631℃).In view of this problem,the reasons and Countermeasures for the superheater overheating of the same type of unit are summarized,and the wall temperature characteristics of the third stage superheater are comprehensively analyzed based on the general situation of the project,this paper puts forward the technical transformation scheme of adding protective tile to the third stage superheater and adding primary air shrinkage hole to the primary air pipe.The results of numerical calculation and temperature field simulation show that increasing the thickness of the tube wall of the third stage superheater can reduce the diameter temperature of the tube wall;and adding primary air duct can optimize the distribution of the primary air flow field,adjust the combustion condition of the furnace and reduce the radiation heat transfer deviation.The operation test shows that the maximum wall temperature of the third stage superheater can be reduced from646℃to 625℃,the number of wall temperature overruns can be changed from more than 100 times to zero overruns,the average main steam temperature can be increased from 592.14℃to 599.52℃,the coal consumption can be reduced by 0.65 g/kw·h,and it is estimated that 4000t of standard coal will be saved in the whole year;the maximum thermal deviation of superheated steam can be reduced from 10.82℃to2.31℃by the primary air shrinkage modification,the maximum thermal deviation of steam is reduced from 6.54℃to 3.16℃,the desuperheating water quantity of superheater is reduced from 93.07 t/h to 60.83 t/h,the desuperheating water quantity of reheater is changed from 44.02 t/h to 2.53 t/h,and the deviation value of NO_xat both sides of SCR inlet is reduced from 31mg/Nm~3to 5mg/Nm~3. |
